Effect of slip bonds due to type 2B von Willebrand Disease on platelet adhesion, aggregation, and contractile forces

项目总结/摘要 血管性血友病（VWD）的特征是血液蛋白血管性血友病因子（VWF）的缺陷 导致无法控制的出血VWF对于初始血小板栓系和随后的血小板聚集是必需的。 粘附在受损的脉管系统上糖蛋白Ib（GPIb）是在血小板表面上发现的受体， 识别VWF的A1结构域。当血管内皮受损时，VWF与暴露的纤维结合， 胶原蛋白和GPIb，将血小板拴在表面。然后，通过整合素α IIB β 3 允许血小板粘附和聚集，形成坚固且稳定的富含血小板的栓塞。GPIb-A1键形成 在高剪切条件下，其特征在于"捕捉"键，这意味着它在高剪切条件下具有更长的寿命。 增加张力的条件。在2B型VWD中，VWF的功能获得性突变导致VWF表达增加。 在低剪切下对血小板结合的亲和力。2B型VWF突变导致自发性血小板结合， 随后不受控制的出血。以前的工作表明，2B型VWD、VWF和GPIb 不再形成捕获键，而是"滑动"键，其特征在于在 增加张力的条件。此外，血小板细胞骨架力可以独立于整合素发挥作用， α IIB β 3通过GPIb-A1键。然而，先前的工作未能完全解释2B型VWD中的滑移粘结如何 影响血小板粘附和血小板栓形成的机制。我假设力的变化- 2B型VWD引起的GPIb-A1键的寿命关系会影响血小板的粘附和聚集 这是由于不能承受细胞骨架力。将测量血小板粘附力和收缩力 在单个血小板水平上使用柔性的，类似于纳米柱的纳米柱，而由一个纳米柱产生的收缩力 使用微流体装置定量血小板聚集体。使用这些方法，我可以描述 血小板栓形成的生物力学受到2B型VWD的影响，进一步解释了出血 表型将来，与止血启动相关的知识可用于诊断或治疗 2B VWD。

PROJECT SUMMARY/ABSTRACT Von Willebrand Disease (VWD) is characterized by a defect in the blood protein von Willebrand Factor (VWF) and leads to uncontrolled bleeding. VWF is necessary for initial platelet tethering and subsequent platelet adhesion to the injured vasculature. Glycoprotein Ib (GPIb) is a receptor found on the platelet surface that recognizes the A1 domain of VWF. When the vascular endothelium is damaged, VWF binds to exposed fibrillar collagen and to GPIb, tethering the platelet to the surface. Then, cytoskeletal forces acting through integrin αIIBβ3 allow platelets to adhere and aggregate, forming a strong and stable platelet-rich plug. The GPIb-A1 bond forms under conditions of high shear and is characterized as a “catch” bond, meaning it has a longer lifetime under conditions of increased tensile force. In type 2B VWD, a gain-of-function mutation to VWF causes an increased affinity for platelet binding at low shear. The type 2B VWF mutation leads to spontaneous platelet binding and subsequently uncontrolled bleeding. Previous work has demonstrated that with type 2B VWD, VWF and GPIb no longer form a catch bond but instead a “slip” bond, which is characterized by a shorter bond lifetime under conditions of increased tensile force. Additionally, platelet cytoskeletal forces can act independently of integrin αIIBβ3 through the GPIb-A1 bond. However, prior work has failed to fully explain how slip bonds in type 2B VWD affect the mechanics of platelet adhesion and platelet plug formation. I hypothesize that changes in the force- lifetime relationship of GPIb-A1 bonds due to type 2B VWD will affect platelet adhesion and aggregation due to an inability to withstand cytoskeletal forces. Platelet adhesion and contractile force will be measured at the single platelet level using flexible, cantilever-like nanoposts, while the contractile force generated by a platelet aggregate will be quantified using a microfluidic device. Using these methods, I can characterize how the biomechanics of platelet plug formation are affected by type 2B VWD, further explaining the bleeding phenotype. In the future, this knowledge relating to hemostasis initiation can be utilized to diagnose or treat type 2B VWD.